Polymorphonuclear leukocytes (PMNL), an important cell in inflammatory responses, possess specific surface receptors for small N-formyl-peptides and other mediators of inflammation that allow the cell to accumulate at inflammatory sites. Accumulation of PMNL at such sites plays a central role in mediating tissue damage in inflammatory disease states, including rheumatoid arthritis, acute glomerulonephritis, arteritis, and acute respiratory distress syndrome. Cytoskeletal and contractile proteins, including actin, myosin and clathrin, appear to interact with cell surface receptors at the cytoplasmic face of the plasma membrane. These interactions play a central role in PMNL functions including chemotaxis, enzyme, and oxidant release. Using a photoactivatable affinity labeling analog of formyl-Nleu-Leu-Phe-Nleu-(125I)-Tyr-Lys, a 60 kilodalton glycoprotein receptor has been labeled in resting cells. Upon activation of the labeled cells with unlabeled formyl-peptide, the receptor label is rapidly converted from a detergent soluble form to a high molecular weight form which can be isolated by Sepharose 4B chromotography. On the basis of preliminary data it is hypothesized that the receptor clusters at the cell surface resulting in a high molecular weight conversion due to transmembrane associations with elements of the membrane cytoskeleton. The goal of this proposal is twofold: (1) Using the photoaffinity label as a marker, the detergent soluble resting receptor-ligand complex together with any other associated proteins will be characterized with respect to physiochemical properties and molecular structure. The transmembrane orientation of the receptor will be explored by comparing receptor assessibility to impermeant probes in intact cells and isolated inside out latex phagosomes. (2) The high molecular weight, high affinity complex will be isolated from stimulated 125I NAHP-peptide labeled PMNL solubilization in detergent. Using sensitive radiolabeling techniques the high molecular weight form of the receptor will be analyzed with respect to composition, identification of the component(s) which interact directly (or indirectly) with the receptor-ligand complex. Finally, the individual components, including the receptor, will be localized in the intact cell at the electron microscopic level by means of specific monoclonal antibodies.